Groundbased optical and radio astrometry of Hipparcos extragalactic link objects

Abstract

The construction of a new extragalactic all-sky reference frame based on groundbased high precision optical and radio astrometry of selected compact radio sources and radio stars has been started in 1987 as a joint longterm project involving several astrometric facilities in both hemispheres. At present this system is based on a masterlist of about 400 extragalactic sources, mostly displaying optical counterparts and about 100 radio stars. A progress report is given with special view to an application for the HIPPARCOS extragalactic reference link.